<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
	</body>
</html>
<script>
	
	let net = 'www.xiaoming.com';
	
	let re = /^(http:\/\/)*www\.*[a-z0-9]+\.(com|cn|com\.cn)$/g;
	
	console.log(re.test(net));
	
</script>